Electrochemical apparatus and electronic apparatus

Abstract

The present application provides an electrochemical apparatus and an electronic apparatus. The electrochemical apparatus comprises an electrolyte, a separator, a positive electrode sheet and a negative electrode sheet; the electrolyte comprises a compound represented by formula (I); based on the mass of the electrolyte, the mass percentage content of the compound represented by formula (I) is A%, where 30≤A≤80; the separator comprises a porous substrate and a porous coating arranged on at least one side of the porous substrate, the porosity of the separator being 25%-35%. The present application regulates and controls the structure of the separator and components of the electrolyte and combines same, such that the OCPD cycle performance of the electrochemical apparatus is improved by means of the synergy of the separator and the electrolyte.

Description

Electrochemical device and electronic device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 3, 2024, with application number 202410009897.8 and invention name “An Electrochemical Device and Electronic Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Art

[0003] Electrochemical devices, such as lithium-ion batteries, have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, and good safety. They are widely used in various fields such as portable energy storage, electronic equipment, and electric vehicles. With the rapid development of the application of lithium-ion batteries in consumer terminals and other fields, the market demand for the performance of lithium-ion batteries is also getting higher and higher, such as OCPD (one cylce per day) cycle performance. The test process of this cycle performance simulates the client's usage habits and is closer to the real usage scenario. However, the OCPD cycle process has high requirements for lithium-ion batteries, and the OCPD cycle performance of existing lithium-ion batteries is not ideal. Therefore, how to improve the OCPD cycle performance of lithium-ion batteries has become a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The purpose of this application is to provide an electrochemical device and an electronic device to improve the OCPD (one cycle per day) performance of the electrochemical device. The specific technical solution is as follows:

[0005] A first aspect of the present application provides an electrochemical device comprising an electrolyte, a separator, a positive electrode sheet, and a negative electrode sheet, wherein the electrolyte comprises a compound represented by formula (I):

[0006] R 11 and R 12 Each independently selected from C1 to C 10 The alkyl group, R 11 and R 12At least one is substituted by fluorine; based on the mass of the electrolyte, the mass percentage of the compound represented by formula (I) is A%, 30≤A≤80; the isolation membrane includes a porous substrate and a porous coating provided on at least one side of the porous substrate, and the porosity of the isolation membrane is 25% to 35%. In the present application, the isolation membrane has a relatively low porosity, which can ensure that the isolation membrane of the electrochemical device has a relatively high mechanical strength, which is beneficial to reduce the probability of internal short circuit of the electrochemical device during actual working conditions, thereby improving the safety performance of the electrochemical device. However, the relatively low porosity of the isolation membrane will reduce the storage space of the electrolyte, reduce the amount of electrolyte retained, and make the electrolyte easily lost, thereby resulting in a blocked lithium ion transmission channel between the positive electrode and the negative electrode, affecting the transmission of lithium ions, and further affecting the OCPD cycle performance of the electrochemical device. Since the compound represented by formula (I) has strong antioxidant properties, it can reduce the oxidation reaction between the positive electrode active material and the electrolyte, widen the oxidation window of the electrolyte, and make the electrochemical device have good positive electrode interface stability, which is beneficial to reduce the consumption rate of the electrolyte and delay the loss rate of the electrolyte, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0007] In some embodiments of the present application, 40≤A≤75. By regulating the value of A within the above range, the compound represented by formula (I) can be more effectively exerted, and the electrochemical device can have good positive electrode interface stability, which can further reduce the consumption rate of the electrolyte and delay the loss rate of the electrolyte. This can further improve the OCPD cycle performance of the electrochemical device while ensuring the safety performance of the electrochemical device.

[0008] In some embodiments of the present application, the porosity of the separator is 25% to 30%. The lower porosity of the separator ensures that the separator of the electrochemical device has higher mechanical strength, which helps to further reduce the probability of internal short circuits in the electrochemical device during actual operation, thereby further improving the safety of the electrochemical device.

[0009] In some embodiments of the present application, the compound represented by formula (I) includes at least one of the following compounds:

[0010] In the electrochemical device of the present application, the electrolyte includes the compound represented by formula (I) within the above range, which can better exert the effect of the compound represented by formula (I), so that the electrochemical device has good positive electrode interface stability, which is beneficial to reducing the consumption rate of the electrolyte and delaying the loss efficiency of the electrolyte, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0011] In some embodiments of the present application, the electrolyte includes a non-fluorinated carboxylate, wherein the non-fluorinated carboxylate includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; the mass percentage of the non-fluorinated carboxylate is B%, based on the mass of the electrolyte, and 10≤B≤60. Further introducing the aforementioned non-fluorinated carboxylate into the electrolyte and regulating its mass percentage B% within the aforementioned range can impart an appropriate viscosity to the electrolyte, improve wettability at the positive and negative electrode interfaces, and reduce polarization, thereby enhancing the OCPD cycling performance of the electrochemical device while ensuring safety performance.

[0012] In some embodiments of the present application, the electrolyte includes a cyclic carbonate, wherein the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or vinyl ethylene carbonate; the mass percentage of the cyclic carbonate is C%, 0≤C≤10, based on the mass of the electrolyte. Further introducing the cyclic carbonate into the electrolyte and regulating its mass percentage C% within the above-mentioned range facilitates the dissociation of the lithium salt, improves the conductivity of the electrolyte, facilitates the anion film formation of the lithium salt, adjusts the electrolyte solvation structure, and enhances the stability of the positive and negative electrode interfaces, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0013] In some embodiments of the present application, the electrolyte includes a trinitrile compound, wherein the trinitrile compound includes at least one of 1,3,5-pentanetricarboxylic acid nitrile, 1,2,3-propanetricarboxylic acid nitrile, 1,3,6-hexanetrinitrile, or 1,2,3-tris(2-cyanoethoxy)propane; the mass percentage of the trinitrile compound is D%, based on the mass of the electrolyte, and 1≤D≤3. Further introduction of the aforementioned trinitrile compound into the electrolyte and regulating its mass percentage D% within the aforementioned range can further enhance the stability of the positive electrode interface, thereby improving the OCPD cycling performance of the electrochemical device while ensuring the safety performance of the electrochemical device.

[0014] In some embodiments of the present application, the coating area density of the porous coating is 0.1 mg / 1540.25 mm 2 Up to 10mg / 1540.25mm 2 By regulating the coating area density of the porous coating within the above range, the separator can have a lower porosity and a higher bonding force between the separator and the positive and negative electrode sheets, which is beneficial for reducing the thickness of the electrochemical device. This helps ensure the safety performance of the electrochemical device while ensuring that the electrochemical device has good OCPD cycle performance and improves the volume energy density of the electrochemical device.

[0015] In some embodiments of the present application, the porous coating layer includes inorganic particles and a fluorine-containing binder. Based on the mass of the porous coating layer, the mass ratio of the inorganic particles to the fluorine-containing binder is m, where 1≤m≤2. By regulating the mass ratio m of the inorganic particles to the fluorine-containing binder within the above range, it is possible to achieve a high bonding force between the separator and the positive and negative electrode sheets while utilizing the effects of the inorganic particles and the fluorine-containing binder. This helps reduce the thickness of the electrochemical device and ensures that the separator has an appropriate porosity. This helps ensure the safety performance of the electrochemical device while also ensuring that the electrochemical device has good OCPD cycle performance and increases the volumetric energy density of the electrochemical device.

[0016] In some embodiments of the present application, the inorganic particles include at least one of magnesium hydroxide, boehmite or aluminum oxide, the fluorine-containing binder includes a polyvinylidene fluoride binder, and the polyvinylidene fluoride binder includes at least one of polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene copolymer. The use of the above-mentioned types of inorganic particles can improve the high temperature resistance and heat shrinkage resistance of the isolation membrane and enhance the mechanical strength of the isolation membrane, thereby helping to improve the safety performance of the electrochemical device on the basis of the good OCPD cycle performance of the electrochemical device. The use of the above-mentioned types of fluorine-containing binders can improve the affinity of the electrode plate to the electrolyte and improve the wettability of the electrolyte to the electrode plate, thereby helping to improve the OCPD cycle performance of the electrochemical device while ensuring the safety performance of the electrochemical device.

[0017] In some embodiments of the present application, the inorganic particles are magnesium hydroxide, which has excellent flame retardant properties that can further improve the high temperature resistance and heat shrinkage resistance of the isolation membrane and enhance the mechanical strength of the isolation membrane, thereby facilitating further improving the safety performance of the electrochemical device on the basis of the electrochemical device having good OCPD cycle performance.

[0018] The second aspect of the present application provides an electronic device comprising the electrochemical device provided in the first aspect of the present application. The electrochemical device provided in the present application has good OCPD cycle performance, thereby providing the electronic device provided in the present application with a long service life and good performance.

[0019] Beneficial effects of this application:

[0020] The present application provides an electrochemical device and an electronic device. The electrochemical device includes an electrolyte, a separator, a positive electrode plate, and a negative electrode plate, wherein the electrolyte includes a compound represented by formula (I), and the mass percentage of the compound represented by formula (I) is A%, 30≤A≤80 based on the mass of the electrolyte; the separator includes a porous substrate and a porous coating provided on at least one side of the porous substrate, and the porosity of the separator is 25% to 35%. The separator in the present application has a relatively low porosity, which can ensure that the separator of the electrochemical device has a relatively high mechanical strength, which is beneficial to reducing the probability of internal short circuit of the electrochemical device during actual working conditions, thereby improving the safety of the electrochemical device. However, the relatively low porosity of the separator will reduce the storage space of the electrolyte, reduce the amount of electrolyte retained, and make the electrolyte easily lost, thereby resulting in a blocked lithium ion transmission channel between the positive electrode and the negative electrode, affecting the transmission of lithium ions, and further affecting the OCPD cycle performance of the electrochemical device. Since the compound represented by formula (I) has strong antioxidant properties, it can reduce the oxidation reaction between the positive electrode active material and the electrolyte, widen the oxidation window of the electrolyte, and make the electrochemical device have good positive electrode interface stability, which is beneficial to reduce the consumption rate of the electrolyte and delay the loss rate of the electrolyte, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0021] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0023] It should be noted that, in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0024] Compared to conventional cycling performance testing, the OCPD cycling performance test includes a full charge and full discharge rest period. Therefore, it places higher demands on the stability of the positive and negative electrode interfaces of the electrochemical device. However, existing electrochemical devices suffer from poor positive and negative electrode interface stability, preventing them from achieving ideal OCPD cycling performance. Based on this, the present application provides an electrochemical device and an electronic device.

[0025] A first aspect of the present application provides an electrochemical device comprising an electrolyte, a separator, a positive electrode sheet, and a negative electrode sheet, wherein the electrolyte comprises a compound represented by formula (I):

[0026] R 11 and R 12 Each independently selected from C1 to C 10 The alkyl group, R 11 and R 12 At least one is substituted by fluorine. In some embodiments of the present application, R 11 and R 12 are each independently selected from the following groups which may be substituted or unsubstituted by fluorine: methyl, ethyl or propyl, R 11 and R 12 At least one is substituted by fluorine. Based on the mass of the electrolyte, the mass percentage of the compound represented by formula (I) is A%, 30≤A≤80, preferably, 40≤A≤75; the isolation membrane includes a porous substrate and a porous coating provided on at least one side of the porous substrate, and the porosity of the isolation membrane is 25% to 35%, preferably, the porosity of the isolation membrane is 25% to 30%. For example, A can be 30, 40, 43, 50, 56, 60, 64, 70, 75, 80 or a range consisting of any two of the above values. For example, the porosity of the isolation membrane can be 25%, 27%, 27.5%, 29%, 30%, 31%, 33%, 35% or a range consisting of any two of the above values.

[0027] The present application provides a porous coating on at least one side of the porous substrate of the separator and regulates the porosity of the separator within the above range. The separator has a low porosity, which can ensure that the separator of the electrochemical device has high mechanical strength, which is beneficial to reducing the probability of internal short circuit in the electrochemical device during actual operation, thereby improving the safety performance of the electrochemical device. However, the low porosity of the separator will reduce the storage space of the electrolyte, reduce the amount of electrolyte retained, and make the electrolyte easily lost, thereby causing the lithium ion transmission channel between the positive electrode and the negative electrode to be blocked, affecting the transmission of lithium ions, and further affecting the OCPD cycle performance of the electrochemical device. The present application introduces the compound represented by formula (I) into the electrolyte and regulates its mass percentage A% within the above range. The compound represented by formula (I) has strong antioxidant properties, can reduce the oxidation reaction between the positive electrode active material and the electrolyte, widen the oxidation window of the electrolyte, make the electrochemical device have good positive electrode interface stability, reduce the consumption rate of the electrolyte, and delay the loss rate of the electrolyte, thereby improving the OCPD cycle performance of the electrochemical device. Therefore, the application of the above-mentioned separator and the electrolyte comprising the compound represented by formula (I) to an electrochemical device can improve the OCPD cycle performance of the electrochemical device while ensuring the safety performance of the electrochemical device. When the porosity of the separator is too low, for example, less than 25%, the lithium ion transmission path is insufficient, which is not conducive to improving the OCPD cycle performance of the electrochemical device. When the porosity of the separator is too high, for example, greater than 35%, the separator structure is unstable and the mechanical strength is poor. It cannot resist the puncture of particles on the electrode surface, which can easily cause local short circuits between the positive and negative electrodes, resulting in serious self-discharge problems and affecting the safety performance of the electrochemical device. When A is too low, for example, less than 30, the content of the compound represented by formula (I) is too low and its effect is limited. The effect of enhancing the positive electrode interface stability is weak, and the effect of reducing the electrolyte consumption rate and delaying the electrolyte loss rate is also weak, which is not conducive to improving the OCPD cycle performance of the electrochemical device. When A is too high, for example, greater than 80, the content of the compound represented by formula (I) is too high, which increases the impedance and polarization of the electrochemical device, which is not conducive to improving the OCPD cycle performance of the electrochemical device. In the present application, isolation membranes with different porosities can be obtained by regulating the coating surface density, thickness or formulation composition of the porous coating.

[0028] In some embodiments of the present application, the compound represented by formula (I) includes at least one of the following compounds:

[0029] In the electrochemical device of the present application, the electrolyte includes the compound represented by formula (I) within the above range, which can better exert the effect of the compound represented by formula (I), so that the electrochemical device has good positive electrode interface stability, which is beneficial to reducing the consumption rate of the electrolyte and delaying the loss rate of the electrolyte, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0030] In some embodiments of the present application, the electrolyte includes a non-fluorinated carboxylate, and the non-fluorinated carboxylate includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylate is B%, and 10≤B≤60. For example, B can be 10, 20, 24, 30, 36, 40, 50, 58, 60, or a range consisting of any two of the above values. The viscosity of the compound represented by formula (I) is relatively large, resulting in poor wettability of the electrolyte to the positive electrode interface and the negative electrode interface. The non-fluorinated carboxylic acid ester has a similar structure to the compound represented by formula (I), has good affinity and low viscosity. On the basis of the compound represented by formula (I), the above-mentioned type of non-fluorinated carboxylic acid ester is further introduced and its mass percentage B% is controlled within the above-mentioned range. This can make the electrolyte have a suitable viscosity, improve the wettability of the positive electrode interface and the negative electrode interface, and reduce polarization, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0031] In some embodiments of the present application, the electrolyte includes a cyclic carbonate, and the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or vinyl ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C%, and 0≤C≤10. For example, C can be 0, 2, 3.5, 4, 6, 6.4, 8, 10, or a range consisting of any two of the above values. The compound represented by formula (I) has poor dissociation of lithium salts. On the basis of the compound represented by formula (I), the above-mentioned type of cyclic carbonate is further introduced and its mass percentage C% is regulated within the above range, which is beneficial to the dissociation of lithium salts, improves the conductivity of the electrolyte, and is also beneficial to the anion film formation of lithium salts, adjusts the electrolyte solvation structure, and enhances the stability of the positive electrode interface and the negative electrode interface, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0032] In some embodiments of the present application, the electrolyte includes a trinitrile compound, and the trinitrile compound includes at least one of 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile or 1,2,3-tris(2-cyanoethoxy)propane; based on the mass of the electrolyte, the mass percentage of the trinitrile compound is D%, and 1≤D≤3. For example, D can be 1, 1.4, 1.8, 2, 2.4, 2.8, 3, or a range consisting of any two of the above values. The trinitrile compound can complex with the high-valent metal ions in the positive electrode active material to stabilize the positive electrode interface. On the basis of the compound represented by formula (I), further introducing the above-mentioned type of trinitrile compound and regulating its mass percentage D% within the above range can further enhance the stability of the positive electrode interface, thereby ensuring the safety performance of the electrochemical device while improving the OCPD cycle performance of the electrochemical device.

[0033] In the present application, the electrolyte also includes other organic solvents and other additives. The present application has no particular restrictions on the types of other organic solvents and other additives, as long as the purpose of the present application can be achieved. For example, other organic solvents may include but are not limited to dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, carbon At least one of 1,1,2-trifluoro-2-methylethylenediamine, trifluoromethylethylene carbonate, γ-butyrolactone, decanoic acid, valerolactone, caprolactone, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, trimethyl phosphate, triethyl phosphate or trioctyl phosphate. Other additives may include but are not limited to at least one of succinonitrile, adiponitrile, 1,3-propane sultone, vinyl sulfate and vinylene carbonate.

[0034] In some embodiments of the present application, the sum of the mass percentages of other organic solvents and other additives based on the mass of the electrolyte is E%, and 0≤E≤40. For example, E can be 0, 10, 15, 20, 23, 25, 30, 35, 37, 40, or a range consisting of any two of the foregoing values.

[0035] In the present application, the electrolyte further includes a lithium salt. The present application does not particularly limit the type of lithium salt, as long as the purpose of the present application can be achieved. For example, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, or lithium difluorophosphate. Preferably, the lithium salt includes lithium hexafluorophosphate.

[0036] In some embodiments of the present application, the mass percentage of the lithium salt is F% based on the mass of the electrolyte, and 10≤F≤20. For example, F can be 10, 12, 12.5, 14, 15, 16, 18, 20, or a range consisting of any two of the above values.

[0037] In some embodiments of the present application, the electrolyte may include a lithium salt, a compound represented by formula (I), a cyclic carbonate, other organic solvents, and other additives. The weight percentages of the lithium salt, the compound represented by formula (I), the cyclic carbonate, other organic solvents, and other additives are as described above. The electrochemical device including the above electrolyte has good OCPD cycle performance.

[0038] In some embodiments of the present application, the electrolyte may include a lithium salt, a compound represented by formula (I), a cyclic carbonate, other organic solvents and other additives, and any one of a non-fluorinated carboxylic acid ester and a trinitrile compound. The weight percentages of the lithium salt, the compound represented by formula (I), the cyclic carbonate, other organic solvents and other additives, the non-fluorinated carboxylic acid ester, and the trinitrile compound are as described above. An electrochemical device including the above electrolyte exhibits good OCPD cycling performance.

[0039] In some embodiments of the present application, the electrolyte may include a lithium salt, a compound represented by formula (I), a cyclic carbonate, a non-fluorinated carboxylic acid ester, a trinitrile compound, other organic solvents, and other additives. The mass percentage of the compound represented by formula (I) is 30% to 79%, the mass percentage of the non-fluorinated carboxylic acid ester is 10% to 59%, and the mass percentages of the lithium salt, cyclic carbonate, trinitrile compound, other organic solvents, and other additives are as described above. The electrochemical device including the above electrolyte has good OCPD cycle performance.

[0040] In some embodiments of the present application, the coating area density of the porous coating is 0.1 mg / 1540.25 mm 2 Up to 10mg / 1540.25mm 2 Preferably, the coating area density of the porous coating is 2.5 mg / 1540.25 mm 2 Up to 5mg / 1540.25mm 2 For example, the coating area density of the porous coating can be 0.1 mg / 1540.25 mm2 , 2mg / 1540.25mm 2 , 2.5mg / 1540.25mm 2 、4mg / 1540.25mm 2 、5mg / 1540.25mm 2 、5.7mg / 1540.25mm 2 、6mg / 1540.25mm 2 , 7.4mg / 1540.25mm 2 、8mg / 1540.25mm 2 、10mg / 1540.25mm 2 Or a range consisting of any two of the above values. By regulating the coating area density of the porous coating within the above range, the separator can have a lower porosity, ensuring that the separator of the electrochemical device has a higher mechanical strength, which is beneficial to reducing the probability of internal short circuits in the electrochemical device during actual operating conditions, thereby improving the safety performance of the electrochemical device. At the same time, it is also beneficial to ensure that the separator has a higher adhesion force with the positive electrode sheet and the negative electrode sheet, which is beneficial to reducing the thickness of the electrochemical device, thereby ensuring the safety performance of the electrochemical device while ensuring that the electrochemical device has good OCPD cycle performance and improving the volume energy density of the electrochemical device.

[0041] In some embodiments of the present application, the porous coating includes inorganic particles and a fluorine-containing binder, and the mass ratio of the inorganic particles to the fluorine-containing binder is m, 1≤m≤2, based on the mass of the porous coating. For example, m can be 1, 1.2, 1.4, 1.6, 1.8, 2, or a range consisting of any two of the above values. The viscosity of the compound represented by formula (I) is relatively large, resulting in poor wettability of the electrolyte to the electrode plates. The fluorine-containing binder in the porous coating can improve the affinity of the electrode plates to the electrolyte and improve the wettability of the electrolyte to the electrode plates, which is beneficial to improving the OCPD cycle performance of the electrochemical device. The inorganic particles in the porous coating can improve the high temperature resistance and heat shrinkage resistance of the isolation membrane and enhance the mechanical strength of the isolation membrane, which is beneficial to improving the safety performance of the electrochemical device on the basis of the good OCPD cycle performance of the electrochemical device. By regulating the mass ratio m of the inorganic particles to the fluorine-containing binder within the above range, the inorganic particles and the fluorine-containing binder can be exerted while the isolation membrane and the positive electrode sheet and the negative electrode sheet have a higher bonding force, which is beneficial to reducing the thickness of the electrochemical device and ensuring that the isolation membrane has a suitable porosity, thereby ensuring the safety performance of the electrochemical device while helping the electrochemical device to have good OCPD cycle performance and improve the volume energy density of the electrochemical device.

[0042] In some embodiments of the present application, the inorganic particles include at least one of magnesium hydroxide, boehmite, or aluminum oxide, preferably magnesium hydroxide. The use of the above-mentioned types of inorganic particles can improve the high temperature resistance and heat shrinkage resistance of the isolation membrane and enhance the mechanical strength of the isolation membrane, thereby facilitating the improvement of the safety performance of the electrochemical device on the basis of the good OCPD cycle performance of the electrochemical device. When the inorganic particles are magnesium hydroxide, its excellent flame retardant properties can further improve the high temperature resistance and heat shrinkage resistance of the isolation membrane and enhance the mechanical strength of the isolation membrane, thereby facilitating the improvement of the safety performance of the electrochemical device on the basis of the good OCPD cycle performance of the electrochemical device.

[0043] In some embodiments of the present application, the fluorine-containing binder includes a polyvinylidene fluoride binder, and the polyvinylidene fluoride binder includes at least one of polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene copolymer. The viscosity of the compound represented by formula (I) is relatively large, resulting in poor wettability of the electrolyte to the electrode plate. By selecting the above-mentioned type of fluorine-containing binder, the affinity of the electrode plate to the electrolyte can be improved, and the wettability of the electrolyte to the electrode plate can be improved, thereby ensuring the safety performance of the electrochemical device while helping to improve the OCPD cycle performance of the electrochemical device.

[0044] The porous coating of the present application may further include a wetting agent and an auxiliary binder. Based on the mass of the porous coating, the weight percentage of the inorganic particles may be 25% to 70%, the weight percentage of the fluorine-containing binder may be 20% to 60%, the weight percentage of the wetting agent may be 5% to 10%, and the weight percentage of the auxiliary binder may be 5% to 15%. For example, the mass percentage of the inorganic particles can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range consisting of any two of the above values, the mass percentage of the fluorine-containing binder can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or a range consisting of any two of the above values, the mass percentage of the wetting agent can be 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of the above values, and the mass percentage of the auxiliary binder can be 5%, 7%, 9%, 10%, 12%, 15% or a range consisting of any two of the above values. The present application has no particular limitation on the types of the wetting agent and the auxiliary binder, as long as the purpose of the present application can be achieved. For example, the wetting agent may include but is not limited to at least one of dimethylsiloxane, polyethylene oxide, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer or dioctyl sodium salt of sulfosuccinate, and the auxiliary binder may include but is not limited to ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile or butadiene, or a homopolymer or copolymer obtained by polymerizing at least one of the above monomers.

[0045] The present application has no particular restrictions on the porous substrate of the isolation membrane, as long as the purpose of the present application can be achieved. For example, the material of the porous substrate may include but is not limited to polyethylene, polypropylene, polytetrafluoroethylene-based polyolefin films, polyester films (such as polyethylene terephthalate (PET) films), cellulose films, polyimide films, polyamide films, spandex or aramid films, etc. At least one of the types of porous substrates may include but is not limited to woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, rolled membranes or spinning membranes, etc. In the present application, the thickness of the porous substrate is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness of the porous substrate can be 3μm to 30μm. In the present application, the size of the pore size of the porous substrate is not particularly limited, as long as the purpose of the present application can be achieved, for example, the size of the pore size can be 0.01μm to 1μm.

[0046] This application has no special restrictions on the positive electrode sheet, as long as the purpose of this application can be achieved. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. In this application, the positive electrode active material layer can be provided on one surface of the positive electrode current collector along its own thickness direction, or on two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector or a partial area of ​​the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0047] The present application has no special restrictions on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector). The present application has no special restrictions on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 6μm to 12μm, and the thickness of the positive electrode active material layer is 30μm to 120μm. The present application has no special restrictions on the thickness of the positive electrode sheet, as long as the purpose of the present application can be achieved, for example, the thickness of the positive electrode sheet is 50μm to 250μm.

[0048] The positive electrode active material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance that can reversibly embed and extract active ions such as lithium ions. The positive electrode active material layer can be one layer or more layers, and each layer in the multi-layer positive electrode active material layer can contain the same or different positive electrode active materials. The present application has no particular restrictions on the positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include but is not limited to lithium nickel cobalt manganese oxide (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. The chemical formula of the above-mentioned lithium-rich manganese-based material is LiMnO·LiMO, and M may include Ni, Co or Mn. In the present application, a substance having a different composition than that of the positive electrode active material may be attached to the surface of the positive electrode active material. For example, the surface-attached substance may include, but is not limited to, at least one of aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate, lithium carbonate, calcium carbonate, magnesium carbonate, or carbon. By attaching the above-mentioned substance to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, thereby improving the service life of the electrochemical device.

[0049] The positive electrode active material layer may also include a positive electrode conductive agent and a positive electrode binder. The present application does not particularly limit the types of the positive electrode conductive agent and the positive electrode binder, as long as the purpose of the present application can be achieved. For example, the positive electrode binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon; the positive electrode conductive agent may include, but is not limited to, at least one of a carbon-based material, a metal-based material, or a conductive polymer. For example, the carbon-based material may include, but is not limited to, at least one of natural graphite, artificial graphite, conductive carbon black (Super P), or carbon fiber; the metal-based material may include, but is not limited to, at least one of metal powder, metal fiber, copper, nickel, aluminum, or silver; and the conductive polymer may include, but is not limited to, a polyphenylene derivative. The present application has no particular limitation on the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in the positive electrode active material layer, and can be selected according to actual needs as long as the purpose of the present application can be achieved.

[0050] This application does not impose any particular restrictions on the negative electrode sheet, as long as the purpose of this application can be achieved. For example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In this application, the negative electrode active material layer can be disposed on one surface in the thickness direction of the negative electrode current collector, or on two surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. This application does not impose any particular restrictions, as long as the purpose of this application can be achieved.

[0051] The present application has no special restrictions on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector (such as carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.). In the present application, there is no special restriction on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode current collector is 6μm to 12μm, and the thickness of the negative electrode active material layer is 30μm to 150μm. In the present application, there is no special restriction on the thickness of the negative electrode sheet, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode sheet is 50μm to 350μm.

[0052] The negative electrode active material layer of the present application includes a negative electrode active material. The negative electrode active material layer can be one or more layers. Each layer in the multi-layer negative electrode active material layer can contain the same or different negative electrode active materials. The negative electrode active material is any substance that can reversibly embed and extract active ions such as lithium ions. The negative electrode active material can include but is not limited to graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO x (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate lithiated TiO2-Li4Ti5O 12 , Li-Al alloy and at least one of metallic lithium.

[0053] The negative electrode active material layer in the present application may further include a negative electrode binder and a negative electrode conductor, or the negative electrode active material layer may further include a negative electrode binder, a negative electrode conductor or a thickener. The present application has no particular restrictions on the types of negative electrode binders and negative electrode conductors, as long as the purpose of the present application can be achieved. For example, the negative electrode binder may include but is not limited to at least one of the above-mentioned positive electrode binders, and the negative electrode conductor may include but is not limited to at least one of the above-mentioned positive electrode conductors. The present application has no particular restrictions on the type of thickener, as long as the purpose of the present application can be achieved. For example, the thickener may include but is not limited to at least one of sodium carboxymethyl cellulose or carboxymethyl cellulose.

[0054] The electrochemical device of the present application also includes a packaging bag for containing the positive electrode sheet, separator, negative electrode sheet, and electrolyte, as well as other components of the electrochemical device known in the art. This application does not particularly limit these other components. This application does not particularly limit the packaging bag and can be any packaging bag known in the art, as long as it can achieve the purpose of this application. For example, an aluminum-plastic film packaging bag can be used.

[0055] The electrochemical device of the present application is not particularly limited and may include any device that undergoes an electrochemical reaction. In some embodiments of the present application, the electrochemical device may include, but is not limited to, a lithium-ion battery, a sodium-ion battery, a lithium polymer electrochemical device, or a lithium-ion polymer electrochemical device.

[0056] The preparation process of the electrochemical device is well known to those skilled in the art and is not particularly limited in this application. For example, it may include, but is not limited to, the following steps: stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and winding, folding, and other operations as needed to obtain a wound electrode assembly, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag, and sealing the bag to obtain the electrochemical device; or stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag, and sealing the bag to obtain the electrochemical device. In addition, as needed, overcurrent protection components, guide plates, etc. may be placed in the packaging bag to prevent pressure rise and overcharging and discharging inside the electrochemical device.

[0057] The second aspect of the present application provides an electronic device comprising the electrochemical device according to any of the aforementioned embodiments of the present application. The electrochemical device provided by the present application has good OCPD cycle performance, thereby providing the electronic device provided by the present application with a long service life and good performance.

[0058] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0059] Example

[0060] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0061] Test methods and equipment:

[0062] Test of the porosity of the isolation membrane

[0063] The porosity of the isolation membrane is tested according to the national standard GB / T 21650.1-2008 “Determination of pore size distribution and porosity of solid materials by mercury intrusion porosimetry and gas adsorption method Part 1: Mercury intrusion porosimetry”.

[0064] Testing of coating area density of porous coatings

[0065] The lithium-ion batteries of the examples and comparative examples were discharged at 0.5C to 3.0V, and then disassembled to obtain the separators. The impurities on the separator surface were cleaned with dimethyl carbonate (DMC) and dried at 60°C to obtain the test samples of the separators. An area of ​​S mm was punched out on the test samples of the separators. 2 The small disc is weighed and recorded as m1, and then the porous coating on one side of the small disc is peeled off to obtain the mass of the small disc after the porous coating is peeled off, recorded as m2. The coating surface density of the porous coating = (m1-m2) / S.

[0066] OCPD cycle performance test

[0067] Adjust the test temperature to a constant 25°C. Charge the lithium-ion battery to 4.48V at a constant current of 0.5C, then charge it to 0.05C at a constant voltage of 4.48V, let it rest for 12 hours, and then discharge it to 3.0V at a constant current of 0.2C and let it rest for 5 hours. This is one charge-discharge cycle, with a total time of 24 hours. This is the first cycle, recorded as the discharge capacity of the first cycle. Perform charge-discharge cycles on the lithium-ion battery according to the above method, and record the discharge capacity of each cycle until the discharge capacity of the lithium-ion battery decays to 80% of the discharge capacity of the first cycle. Record the number of charge-discharge cycles and record it as the number of 25°C OCPD cycles.

[0068] 135℃ 1h hot box pass rate test

[0069] At 25°C, the lithium-ion battery was charged to 4.48V at a constant current of 0.7C, and charged to a current of 0.05C at a constant voltage of 4.48V. The lithium-ion battery was placed in a high-temperature box, heated to 135°C at a temperature rise rate of 5±2°C / min, and then maintained for 1 hour, and the changes in the voltage, temperature, and hot box temperature of the lithium-ion battery were recorded. The lithium-ion battery passed the test if it did not catch fire, explode, or smoke. Ten lithium-ion batteries were prepared according to the preparation methods of the various embodiments and comparative examples, and tested according to the above method, and the number of lithium-ion batteries that passed the test was recorded. The safety performance is characterized by the 135°C 1h hot box pass rate. The more lithium-ion batteries that pass the test, the better the safety performance.

[0070] Example 1-1

[0071] <Preparation of Separator>

[0072] A porous polyethylene film with a thickness of 5 μm (provided by Celgard) was used as the porous substrate.

[0073] Inorganic particles of magnesium hydroxide, fluorine-containing binder polyvinylidene fluoride (weight average molecular weight Mw = 1.3 × 10 6), dimethylsiloxane (CH3)2SiO as a wetting agent, and acrylonitrile as an auxiliary binder were mixed in a mass ratio of 51:34:10:5, deionized water was added as a solvent, and stirred evenly to form a porous coating slurry with a solid content of 12 wt%. The porous coating slurry was applied to one surface of the porous substrate with a coating density of 3.3 mg / 1540.25 mm 2 After drying, a porous coating layer is formed on one surface of the porous substrate. The porous coating layer slurry is then applied to the other surface of the porous substrate at the same coating density and dried to form a separator having porous coating layers on both surfaces. The separator has a porosity of 30% and a mass ratio of inorganic particles to fluorine-containing binder, m, of 1.5.

[0074] <Preparation of Electrolyte>

[0075] In an argon atmosphere glove box with a water content of less than 10 ppm, the cyclic carbonate ethylene carbonate (EC), the cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) were mixed in a mass ratio of 10:10:80 to obtain a base solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) and the compound represented by formula (I) (Formula (I-3)) were added to the base solvent and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%, the mass percentage of the compound represented by formula (I-3) was 30%, and the remainder was the base solvent.

[0076] <Preparation of positive electrode sheet>

[0077] The positive electrode active material LiCoO2, the positive electrode conductive agent conductive carbon black (Super P), the positive electrode binder polyvinylidene fluoride (PVDF, Mw = 7 × 10 6 ) are mixed in a mass ratio of 97.5:1:1.5, N-methylpyrrolidone (NMP) is added as a solvent, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry with a solid content of 75wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, dried at 85°C, and cold pressed to obtain a positive electrode sheet with a single-sided coating of a positive electrode active material layer with a thickness of 50μm. Thereafter, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of a positive electrode active material layer. After cutting and welding the positive electrode aluminum tabs, a positive electrode sheet with a specification of 74mm×851mm is obtained for standby use.

[0078] <Preparation of negative electrode sheet>

[0079] The negative electrode active material artificial graphite, negative electrode conductive agent Super P, thickener carboxymethyl cellulose (CMC-Na, Mw = 7 × 10 5), negative electrode binder styrene-butadiene rubber (SBR, Mw = 5 × 10 6 ) were mixed in a mass ratio of 97.5:1:0.5:1, and then deionized water was added as a solvent and stirred evenly in a vacuum mixer to obtain a negative electrode slurry with a solid content of 50 wt%. The negative electrode slurry was evenly coated on one surface of an 8 μm thick negative electrode current collector copper foil, dried at 85°C, and cold pressed to obtain a negative electrode sheet coated on one side with a 60 μm thick negative electrode active material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode active material layer. The sheet was then cut and welded to the negative electrode nickel tab to obtain a negative electrode sheet with a size of 76 mm × 867 mm for future use.

[0080] <Preparation of lithium-ion batteries>

[0081] The negative electrode sheet, separator, and positive electrode sheet prepared above are stacked and wound in sequence to form a wound electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. The lithium-ion battery is produced through vacuum packaging, static standing, formation (charging at a constant current of 0.3C to 3.5V, then charging at a constant current of 1C to 3.9V), capacity evaluation, degassing, and trimming.

[0082] Example 1-2 to Example 1-5

[0083] The preparation was the same as in Example 1-1, except that the mass percentage A% of the compound of formula (I-3) in the "Electrolyte Preparation" was adjusted according to Table 1. When the mass percentage A% of the compound of formula (I-3) was changed, the mass percentage of the base solvent also changed, while the mass ratio of EC, PC, and DEC and the mass percentage of the lithium salt remained unchanged.

[0084] Example 1-6 to Example 1-9

[0085] Except that the coating area density of the porous coating layer and the porosity of the separator were adjusted according to Table 1 in <Preparation of Separator>, the rest were the same as in Example 1-3.

[0086] Example 1-10 to Example 1-12

[0087] Except that the type of the compound represented by formula (I) was adjusted according to Table 1 in <Preparation of Electrolyte>, the rest was the same as Example 1-3.

[0088] Example 2-1

[0089] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0090] <Preparation of Electrolyte>

[0091] In an argon atmosphere glove box with a water content of less than 10 ppm, cyclic carbonate ethylene carbonate (EC), cyclic carbonate propylene carbonate (PC), and other organic solvent diethyl carbonate (DEC) are mixed in a mass ratio of 10:10:80 to obtain a base solvent, and then lithium salt lithium hexafluorophosphate (LiPF6), compound represented by formula (I) (Formula (I-3), and non-fluorinated carboxylic acid ester propyl propionate are added to the base solvent and mixed to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage of lithium salt LiPF6 is 12.5%, the mass percentage A% of the compound represented by formula (I-3) is 65%, the mass percentage B% of propyl propionate is 10%, and the remainder is the base solvent.

[0092] Example 2-2

[0093] The preparation process was the same as in Example 2-1, except that the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of propyl propionate were adjusted according to Table 2 in the "Preparation of Electrolyte Solution". When the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of propyl propionate were changed, the mass ratio of EC, PC, and DEC, the mass percentage of the base solvent, and the mass percentage of the lithium salt remained unchanged.

[0094] Example 2-3

[0095] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0096] <Preparation of Electrolyte>

[0097] In an argon atmosphere glove box with a water content of less than 10 ppm, the compound represented by formula (I) (formula (I-3)) and the non-fluorinated carboxylic acid ester propyl propionate were mixed in a mass ratio of 30:57.5, and then lithium hexafluorophosphate (LiPF6) was added and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%, with the remainder being the compound represented by formula (I-3) and propyl propionate.

[0098] Example 2-4 to Example 2-5

[0099] Except for adjusting the type of non-fluorinated carboxylic acid ester according to Table 2 in <Preparation of Electrolyte>, the rest was the same as Example 2-2.

[0100] Examples 2-6

[0101] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0102] <Preparation of Electrolyte>

[0103] In an argon atmosphere glove box with a water content of less than 10 ppm, cyclic carbonate ethylene carbonate (EC), cyclic carbonate propylene carbonate (PC), and other organic solvent diethyl carbonate (DEC) are mixed in a mass ratio of 10:10:80 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6), a compound represented by formula (I) (Formula (I-3), and a trinitrile compound 1,3,6-hexanetrinitrile are added to the base solvent and mixed to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of the lithium salt LiPF6 is 12.5%, the mass percentage of the compound represented by formula (I-3) is 50%, the mass percentage of 1,3,6-hexanetrinitrile is 1%, and the remainder is the base solvent.

[0104] Example 2-7 to Example 2-8

[0105] The same procedures as in Example 2-6 were followed, except that the mass percentage D% of 1,3,6-hexanetricarbonitrile was adjusted according to Table 2. When the mass percentage D% of 1,3,6-hexanetricarbonitrile was changed, the mass percentage of the base solvent was changed accordingly, while the mass ratio of EC, PC, and DEC, the mass percentage of the lithium salt, and the mass percentage A% of the compound of formula (I-3) remained unchanged.

[0106] Examples 2-9

[0107] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0108] <Preparation of Electrolyte>

[0109] In an argon atmosphere glove box with a water content of less than 10 ppm, cyclic carbonate ethylene carbonate (EC), cyclic carbonate propylene carbonate (PC), and other organic solvent diethyl carbonate (DEC) are mixed in a mass ratio of 10:10:80 to obtain a base solvent, and then lithium salt lithium hexafluorophosphate (LiPF6), compound represented by formula (I) (Formula (I-3), non-fluorinated carboxylic acid ester propyl propionate, and trinitrile compound 1,3,6-hexanetrinitrile are added to the base solvent and mixed to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage content of lithium salt LiPF6 is 12.5%, the mass percentage content A% of the compound represented by formula (I-3) is 49%, the mass percentage content C% of propyl propionate is 25%, the mass percentage content D% of 1,3,6-hexanetrinitrile is 1%, and the remainder is the base solvent.

[0110] Example 2-10 to Example 2-11

[0111] The preparation process was the same as Example 2-9, except that the mass percentage A% of the compound of formula (I-3) and the mass percentage D% of 1,3,6-hexanetricarbonitrile were adjusted according to Table 2 in the "Preparation of Electrolyte Solution". When the mass percentage A% of the compound of formula (I-3) and the mass percentage D% of 1,3,6-hexanetricarbonitrile were changed, the mass ratio of EC, PC, and DEC, the mass percentage of the base solvent, the mass percentage of the lithium salt, and the mass percentage B% of propyl propionate remained unchanged.

[0112] Example 2-12

[0113] Except for adjusting the type of trinitrile compound according to Table 2 in <Preparation of Electrolyte>, the rest is the same as Example 2-10.

[0114] Example 2-13

[0115] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0116] <Preparation of Electrolyte>

[0117] In an argon atmosphere glove box with a water content of less than 10 ppm, the compound represented by formula (I) (formula (I-3)) and the non-fluorinated carboxylic acid ester propyl propionate were mixed in a mass ratio of 50:37.5, and then lithium hexafluorophosphate (LiPF6) was added and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%, with the remainder being the compound represented by formula (I-3) and propyl propionate.

[0118] Example 3-1

[0119] In addition to the inorganic magnesium hydroxide particles and the fluorine-containing binder polyvinylidene fluoride (weight average molecular weight Mw = 1.3 × 10 6 ), a wetting agent dimethylsiloxane (CH3)2SiO, and an auxiliary binder acrylonitrile are mixed in a mass ratio of 42.5:42.5:10:5, and the mass ratio of the inorganic particles to the fluorine-containing binder is m=1, and the rest is the same as in Example 1-3.

[0120] Example 3-2

[0121] In addition to the inorganic magnesium hydroxide particles and the fluorine-containing binder polyvinylidene fluoride (weight average molecular weight Mw = 1.3 × 10 6 ), a wetting agent dimethylsiloxane (CH3)2SiO, and an auxiliary binder acrylonitrile are mixed in a mass ratio of 56.6:28.4:10:5, and the mass ratio of the inorganic particles to the fluorine-containing binder is m=2, and the rest is the same as in Example 1-3.

[0122] Example 3-3 to Example 3-4

[0123] Except for adjusting the parameters in <Preparation of Isolation Film> according to Table 3, the rest is the same as Example 1-3.

[0124] Comparative Example 1 and Comparative Example 2

[0125] Except for adjusting the coating area density of the porous coating layer and the porosity of the separator in <Preparation of Separator>, the rest is the same as Example 1-3.

[0126] Comparative Example 3

[0127] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-1.

[0128] <Preparation of Electrolyte>

[0129] In an argon atmosphere glove box with a water content of less than 10 ppm, the cyclic carbonates ethylene carbonate (EC), cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) were mixed in a mass ratio of 10:10:80 to obtain a base solvent. The lithium salt lithium hexafluorophosphate (LiPF6) was then added to the base solvent and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%, with the remainder being the base solvent.

[0130] Comparative Example 4 to Comparative Example 5

[0131] The preparation was the same as in Example 1-1, except that the mass percentage A% of the compound of formula (I-3) in the "Electrolyte Preparation" was adjusted according to Table 1. When the mass percentage A% of the compound of formula (I-3) was changed, the mass percentage of the base solvent also changed, while the mass ratio of EC, PC, and DEC and the mass percentage of the lithium salt remained unchanged.

[0132] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 3.

[0133] Table 1

[0134] Note: "\" in Table 1 indicates no corresponding parameter. Taking the 135°C 1-h hot box pass rate data for Examples 1-3 in Table 1 as an example, 8 / 10 means that 8 out of 10 lithium-ion batteries passed the hot box test. The same applies to the other examples.

[0135] As can be seen from Examples 1-1 to 1-12 and Comparative Examples 1 to 5, the lithium-ion batteries of the present embodiments, by adding the compound represented by Formula (I) to the electrolyte at a mass percentage A% within the range of the present application, and providing a porous coating on at least one side of the porous substrate in the separator, with the separator having a porosity within the range of the present application, achieve a greater number of 25°C OCPD cycles and a higher 135°C 1-h hot box pass rate. This demonstrates that the lithium-ion batteries exhibit good OCPD cycle performance and safety. However, the porosity of the separators of the lithium-ion batteries of Comparative Examples 1 and 2 is not within the scope of the present application; the electrolyte of the lithium-ion battery of Comparative Example 3 does not include the compound represented by formula (I); the mass percentage A% of the compound represented by formula (I) in the electrolyte of the lithium-ion batteries of Comparative Examples 4 and 5 is not within the scope of the present application. The lithium-ion batteries of Comparative Examples 1 to 5 have a smaller number of 25°C OCPD cycles and a lower 135°C 1h hot box pass rate, indicating that the OCPD cycle performance and safety performance of the lithium-ion batteries are worse.

[0136] The mass percentage A% of the compound represented by formula (I) usually affects the OCPD cycle performance and safety performance of the lithium-ion battery. It can be seen from Examples 1-1 to 1-5 and Comparative Examples 3 to 5 that when A is too small, such as Comparative Examples 3 and 4, the compound represented by formula (I) has limited effect, and the number of 25°C OCPD cycles of the lithium-ion battery is smaller; when A is too large, such as Comparative Example 5, the excessive amount of the compound represented by formula (I) increases the impedance of the lithium-ion battery, increases polarization, and the number of 25°C OCPD cycles is smaller. This indicates that the OCPD cycle performance of the lithium-ion battery is worse. When A is within the range of this application, it is conducive to the effect of the compound represented by formula (I), and the lithium-ion battery has a larger number of 25°C OCPD cycles. This indicates that the OCPD cycle performance of the lithium-ion battery is good. At the same time, the lithium-ion battery also has a high 135°C 1h hot box pass rate, indicating that the safety performance of the lithium-ion battery is good.

[0137] The porosity of the separator generally affects the OCPD cycle performance and safety performance of lithium-ion batteries. As can be seen from Examples 1-3, 1-6, 1-9, and Comparative Examples 1 and 2, when the separator porosity is too low, such as in Comparative Example 1, the lithium ion transmission pathway in the lithium-ion battery is insufficient, resulting in a lower 25°C OCPD cycle number for the lithium-ion battery. When the separator porosity is too high, such as in Comparative Example 2, the separator structure becomes unstable, mechanical strength is poor, and self-discharge problems are severe, resulting in a lower 25°C OCPD cycle number and a lower 135°C 1h hot box pass rate for the lithium-ion battery. This indicates that the OCPD cycle performance and safety performance of the lithium-ion battery are worse. When the separator porosity is within the range of this application, the lithium-ion battery has a greater 25°C OCPD cycle number, indicating good OCPD cycle performance. At the same time, the lithium-ion battery also has a higher 135°C 1h hot box pass rate, indicating good safety performance.

[0138] The type of compound represented by formula (I) generally affects the OCPD cycle performance and safety performance of lithium-ion batteries. As can be seen from Examples 1-3, 1-10, and 1-12, when the electrolyte of the lithium-ion battery includes the compound represented by formula (I) within the scope of this application, it is beneficial to exert the effect of the compound represented by formula (I), and the lithium-ion battery has a large number of 25°C OCPD cycles, indicating that the lithium-ion battery has good OCPD cycle performance. At the same time, the lithium-ion battery also has a high 135°C 1h hot box pass rate, indicating that the lithium-ion battery has good safety performance.

[0139] Table 2

[0140] Note: "\" in Table 2 indicates no corresponding parameter. Taking the 135°C 1-h hot box pass rate data for Examples 1-3 in Table 2 as an example, 8 / 10 means that 8 out of 10 lithium-ion batteries passed the hot box test. The same applies to the other examples.

[0141] The mass percentage B% of non-fluorinated carboxylates usually affects the OCPD cycle performance and safety performance of lithium-ion batteries. It can be seen from Examples 1-3, 2-1 to 2-2 that when the electrolyte of the lithium-ion battery includes the compound represented by formula (I) and a cyclic carbonate, and the non-fluorinated carboxylates are further introduced, and the mass percentage B% thereof is regulated within the scope of this application, the lithium-ion battery has a greater number of 25°C OCPD cycles, indicating that the OCPD cycle performance of the lithium-ion battery is good. This is because the viscosity of the non-fluorinated carboxylates is relatively low. Further introducing the non-fluorinated carboxylates into the electrolyte and regulating the mass percentage B% thereof within the scope of this application can improve the problem of the high viscosity of the compound represented by formula (I) so that the electrolyte has a suitable viscosity, improve the wettability of the positive electrode interface and the negative electrode interface, reduce polarization, and thus enable the lithium-ion battery to have good OCPD cycle performance. At the same time, the lithium-ion battery also has a relatively high 135°C 1h hot box pass rate, indicating that the safety performance of the lithium-ion battery is good.

[0142] The type of non-fluorinated carboxylates usually affects the OCPD cycle performance and safety performance of lithium-ion batteries. It can be seen from Examples 1-3, 2-2, 2-4 to 2-5 that when the electrolyte of the lithium-ion battery includes the compound represented by formula (I) and a cyclic carbonate, and a non-fluorinated carboxylate is further introduced, and a non-fluorinated carboxylate within the scope of the present application is selected, the lithium-ion battery has a greater number of 25°C OCPD cycles, indicating that the OCPD cycle performance of the lithium-ion battery is good. This is because the viscosity of the non-fluorinated carboxylates is relatively low. Further introduction of non-fluorinated carboxylates within the scope of the present application into the electrolyte can improve the problem of the high viscosity of the compound represented by formula (I) so that the electrolyte has a suitable viscosity, improves the wettability of the positive electrode interface and the negative electrode interface, reduces polarization, and thus enables the lithium-ion battery to have good OCPD cycle performance. At the same time, the lithium-ion battery also has a relatively high 135°C 1h hot box pass rate, indicating that the safety performance of the lithium-ion battery is good.

[0143] The mass percentage D% of the trinitrile compound usually affects the OCPD cycle performance and safety performance of the lithium-ion battery. It can be seen from Examples 1-3, 2-6 to 2-8 that when the electrolyte of the lithium-ion battery includes the compound shown in formula (I) and the cyclic carbonate, the trinitrile compound is further introduced, and its mass percentage D% is regulated within the scope of this application, the lithium-ion battery has a larger 25°C OCPD cycle number, indicating that the OCPD cycle performance of the lithium-ion battery is good. This is because the trinitrile compound can stabilize the positive electrode interface. Further introducing the trinitrile compound into the electrolyte and regulating its mass percentage D% within the scope of this application can further enhance the stability of the positive electrode interface, thereby enabling the lithium-ion battery to have good OCPD cycle performance. At the same time, the lithium-ion battery also has a higher 135°C 1h hot box pass rate, indicating that the safety performance of the lithium-ion battery is good.

[0144] It can be seen from Examples 1-3, 2-9 to 2-11 that when the electrolyte of the lithium-ion battery includes the compound represented by formula (I) and a cyclic carbonate, and further introduces a non-fluorinated carboxylic acid ester and a trinitrile compound, the lithium-ion battery has a greater number of 25°C OCPD cycles, indicating that the OCPD cycle performance of the lithium-ion battery is good. The compound represented by formula (I) has good compatibility and superposition with the cyclic carbonate, the non-fluorinated carboxylic acid ester and the trinitrile compound. The above combination of substances is applied to lithium-ion batteries, which is more conducive to making the lithium-ion battery have good OCPD cycle performance. At the same time, the lithium-ion battery also has a high 135°C 1h hot box pass rate, indicating that the safety performance of the lithium-ion battery is good.

[0145] The type of trinitrile compound usually affects the OCPD cycle performance of the lithium-ion battery. It can be seen from Examples 2-10 and 2-12 that when the lithium-ion battery selects the trinitrile compound within the scope of this application, the lithium-ion battery has a larger 25°C OCPD cycle number, indicating that the OCPD cycle performance of the lithium-ion battery is good. This is because the trinitrile compound can stabilize the positive electrode interface. Further introduction of the trinitrile compound within the scope of this application into the electrolyte can further enhance the stability of the positive electrode interface, thereby enabling the lithium-ion battery to have good OCPD cycle performance. At the same time, the lithium-ion battery also has a higher 135°C 1h hot box pass rate, indicating that the safety performance of the lithium-ion battery is good.

[0146] As can be seen from Examples 1-3, 2-3, and 2-13, when the lithium-ion battery electrolyte includes the compound represented by Formula (I) and a non-fluorinated carboxylate, but does not include a cyclic carbonate, the lithium-ion battery exhibits a greater number of 25°C OCPD cycles, indicating good OCPD cycling performance. Furthermore, the lithium-ion battery also exhibits a high 135°C 1-hour hot box pass rate, demonstrating good safety performance.

[0147] Table 3

[0148] Note: Taking the 135°C 1h hot box pass rate data of Examples 1-3 in Table 3 as an example, 8 / 10 means that 8 out of 10 lithium-ion batteries passed the hot box test. The same applies to other examples.

[0149] The mass ratio m of inorganic particles to fluorine-containing binder usually affects the OCPD cycle performance and safety performance of lithium-ion batteries. It can be seen from Examples 1-3, 3-1 to 3-2 that when m is within the scope of this application, the lithium-ion battery has a larger number of 25°C OCPD cycles, indicating that the OCPD cycle performance of the lithium-ion battery is good. This is because the viscosity of the compound represented by formula (I) in the electrolyte is relatively large, resulting in poor wettability of the electrolyte to the electrode pole piece, while the fluorine-containing binder in the porous coating can increase the affinity of the electrode pole piece to the electrolyte and improve the wettability of the electrolyte to the electrode pole piece, thereby enabling the lithium-ion battery to have good OCPD cycle performance. At the same time, the lithium-ion battery also has a relatively high 135°C 1h hot box pass rate, indicating that the safety performance of the lithium-ion battery is good.

[0150] The type of inorganic particles generally affects the OCPD cycling performance and safety of lithium-ion batteries. As shown in Examples 1-3 and 3-3, when the inorganic particle types fall within the range of this application, the lithium-ion batteries achieve a high number of 25°C OCPD cycles, indicating good OCPD cycling performance. Furthermore, the batteries also exhibit a high 135°C 1-hour hot box pass rate, demonstrating good safety.

[0151] The type of fluorinated binder generally affects the OCPD cycling performance and safety of lithium-ion batteries. Examples 1-3 and 3-4 show that when the type of fluorinated binder falls within the range of this application, the lithium-ion batteries achieve a high number of 25°C OCPD cycles, indicating good OCPD cycling performance. Furthermore, the batteries also exhibit a high 135°C 1-hour hot box pass rate, demonstrating good safety.

[0152] It should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method or article.

[0153] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0154] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device, which comprises an electrolyte, a separator, a positive electrode plate and a negative electrode plate, wherein, The electrolyte includes a compound represented by formula (I): R 11 and R 12 each independently selected from C1 to C alkyl which may or may not be substituted with fluorine, 10 R 11 and R 12 at least one of them is substituted with fluorine; Based on the mass of the electrolyte, the mass percentage content of the compound shown in formula (I) is A%, and 30 ≤ A ≤ 80; The separator includes a porous substrate and a porous coating provided on at least one side of the porous substrate, and the porosity of the separator is 25% to 35%.

2. The electrochemical device according to claim 1, wherein, 40≤A≤75。 3. The electrochemical device according to claim 1, wherein, The porosity of the separator is 25% to 30%.

4. The electrochemical device according to claim 1, wherein, The compound represented by the formula (I) includes at least one of the following compounds:

5. The electrochemical device according to any one of claims 1 to 4, wherein, The electrolyte includes non-fluorinated carboxylate esters, and the non-fluorinated carboxylate esters include at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate or propyl propionate; Based on the mass of the electrolyte, the mass percentage content of the non-fluorinated carboxylate ester is B%, and 10 ≤ B ≤ 60.

6. The electrochemical device according to any one of claims 1 to 4, wherein, The electrolyte includes cyclic carbonates, and the cyclic carbonates include at least one of ethylene carbonate, propylene carbonate, butylene carbonate or vinylene carbonate; Based on the mass of the electrolyte, the mass percentage content of the cyclic carbonate is C%, and 0 ≤ C ≤ 10.

7. The electrochemical device according to any one of claims 1 to 4, wherein The electrolyte includes trinitrile compounds, and the trinitrile compounds include at least one of 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile or 1,2,3-tris(2-cyanoethoxy)propane; Based on the mass of the electrolyte, the mass percentage content of the trinitrile compound is D%, and 1 ≤ D ≤ 3.

8. The electrochemical device according to any one of claims 1 to 4, wherein, The unit coating weight of the porous coating is 0.1 mg / 1540.25 mm 2 to 10 mg / 1540.25 mm 2 .

9. The electrochemical device according to any one of claims 1 to 4, wherein, The porous coating includes inorganic particles and a fluorine-containing binder, and based on the mass of the porous coating, the mass ratio of the inorganic particles to the fluorine-containing binder is m, and 1 ≤ m ≤ 2.

10. The electrochemical device according to claim 9, wherein, The inorganic particles include at least one of magnesium hydroxide, boehmite or aluminum oxide, and the fluorine-containing binder includes a polyvinylidene fluoride-based binder, and the polyvinylidene fluoride-based binder includes at least one of polyvinylidene fluoride or a polyvinylidene fluoride-hexafluoropropylene copolymer.

11. The electrochemical device according to claim 10, wherein, The inorganic particle is magnesium hydroxide.

12. An electronic device, comprising the electrochemical device according to any one of claims 1 to 11.

Images